Power semiconductor module for improved heat dissipation and power density, and method for manufacturing the same

ABSTRACT

The present disclosure relates to a semiconductor module, especially a power semiconductor module, in which the heat dissipation is improved and the power density is increased. The semiconductor module may include at least two electrically insulating substrates, each having a first main surface and a second main surface opposite to the first main surface. On the first main surface of each of the substrates, at least one semiconductor device is mounted. An external terminal is connected to the first main surface of at least one of the substrates. The substrates are arranged opposite to each other so that their first main surfaces are facing each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/EP2017/071429, filed on Aug. 25, 2017, the disclosure of which ishereby incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a semiconductor module, especially apower semiconductor module.

BACKGROUND

One of the key issues of power modules is the heat removal from thesemiconductor devices comprised therein such as insulated-gate bipolartransistors (IGBTs), metal-oxide-semiconductor field-effect transistors(MOSFETs), diodes etc. Usually, the top side of the semiconductordevices is used to make the electrical connection to the connection padsof the device whereas the bottom side is used to remove the heat byattaching it to a thermally conductive, but electrically isolatingmaterial like a ceramic substrate. In a classical setup, a power modulehas a cooling plate on the bottom side, and the electrical contacts onthe top side.

To further reduce the thermal resistance of the module, the top side ofthe semiconductor device may also be used to remove heat by attaching athermally conductive material, e.g. a copper block. An example for sucha module is described in JP 2008/186890 A. In an embodiment thereof, twosemiconductor devices are held between two heat dissipation plates whoseinner faces face each other, and they are encapsulated by a mold resinin a manner that the heat dissipation plates and the semiconductordevices are enclosed. The outer faces of the heat dissipation plates areexposed from the mold resin. The semiconductor elements are mounted onone of the heat dissipation plates and connected via a spacer to theother heat dissipation plate.

Such a module is also described in Andreas Grassmann, Ottmar Geitner,Wolfram Hable, Christian Neugirg, Alexander Schwarz, Frank Winter, InpilYoo: “Double Sided Cooled Module concept for High Power Density in HEVApplications”, PCIM Europe 2015, 19-21 May 2015, Nuremberg, Germany,pages 442 to 448. The power module combines double sided chip coolingwith electrical isolation of the heat sinks. Electrical isolation isprovided by direct copper bonded (DCB) ceramic substrates. Heat istransported to the lower heat sink by soldering the chip directly ontothe substrate, and to the upper heat sink by spacers which adjust theheight of the module.

However, the production of such double-sided cooled modules is prettyexpensive and the actual reduction of the thermal resistance is only inthe range of 20 to 30%. A reason is that the cooling through the topside of the semiconductor device is less efficient than through thebottom side since the top side is also used for electrical contact.Therefore, the spacer cannot be mounted across the entire top side ofthe semiconductor device. Care has to be taken while mounting the spacernot to damage the electrical connections on the top side of thesemiconductor device.

SUMMARY

It is therefore an object of the present disclosure to provide asemiconductor module, especially a power semiconductor module, having animproved heat dissipation and/or an increased power density.

The foregoing and other objects are achieved by the features of theindependent claims. Further embodiments are apparent from the dependentclaims, the descriptions and the figures.

According to a first aspect, a semiconductor module is provided,comprising at least two electrically insulating substrates, each havinga first main surface and a second main surface opposite to the firstmain surface. For each of the substrates, at least one semiconductordevice is mounted on the first main surface of the correspondingsubstrate. An external terminal is connected to the first main surfaceof at least one of the substrates. The substrates are arranged oppositeto each other so that their first main surfaces are facing each other.

By this arrangement, it is possible, for example, to efficientlydissipate heat generated by the semiconductor devices from the oppositesides of the module. Further, by the improved heat dissipation and thearrangement of semiconductor devices at opposite sides of the module,the power density of a semiconductor module may be improved. Since thesemiconductor devices are only attached single-sided to the substrates,cost and process complexity can be kept low. The modules can bemanufactured using well established assembling technologies andtherefore are potentially low-cost.

In an embodiment of the first aspect, the semiconductor module furthercomprises an encapsulation, and the second main surfaces of each of thesubstrates are exposed on opposite sides of the encapsulation.

Thereby it is possible, for example, to protect the devices by anencapsulation and nevertheless be able to efficiently dissipate heatgenerated by the semiconductor devices from the opposite sides of themodule.

In a further embodiment of the first aspect, the substrates arethermally conductive.

Thereby it is possible, for example, to better conduct heat dissipatedfrom the semiconductor devices to the outside of the module.

In a further embodiment of the first aspect, the at least onesemiconductor device is a power semiconductor device.

Thereby it is possible, for example, to apply the disclosure to powermodules for which efficiently dissipating heat is of a specialimportance.

In a further embodiment of the first aspect, a heat sink is mounted toat least one of the second main surfaces of the substrates.

Thereby it is possible, for example, to further increase the efficiencyof dissipating heat from the semiconductor devices.

In a further embodiment of the first aspect, the external terminalcomprises at least two external leads. All the external leads protrudein a plane from two opposite sides of the module, or all the externalleads protrude from a single side of the module, only.

Thereby it is possible, for example, to provide the connections to themodule in a plane at two opposite sides, which is a commonly usedarrangement for semiconductor devices, or to provide the connections tothe module on one side, only, leaving the other sides free for means fordissipating the heat.

In a further embodiment of the first aspect, the external terminal isformed as a lead frame connected to at least two substrates.

Thereby it is possible, for example, to provide a variant of thesemiconductor module according to the disclosure.

In a further embodiment of the first aspect, the at least two substratesare electrically interconnected by means of bridges between individualleads of the lead frame.

Thereby it is possible, for example, to easily provide interconnectionsbetween the at least two substrates.

In a further embodiment of the first aspect, the external terminal isformed as two separate lead frame s, each connected to one of the atleast two substrates.

Thereby it is possible, for example, to provide another variant of thesemiconductor module according to the disclosure.

In a further embodiment of the first aspect, the at least two substratesare electrically interconnected by means of individual leads of the twoseparate lead frame s being connected to each other.

Thereby it is possible, for example, to easily provide interconnectionsbetween the at least two substrates.

In a further embodiment of the first aspect, the external terminal isformed as pins connected to one of the at least two substrates andprotruding from the module at the side opposite to the substrate towhich the pins are connected.

Thereby it is possible, for example, to provide another variant of thesemiconductor module according to the disclosure.

In a further embodiment of the first aspect, the at least two substratesare electrically interconnected by means of an internal lead frame or bymeans of internal pins.

Thereby it is possible, for example, to easily provide interconnectionsbetween the at least two substrates.

In a further embodiment of the first aspect, the at least two substratesare arranged spaced apart from each other.

Thereby it is possible, for example, to avoid that the semiconductordevices or other components at the first sides of the substrates contacteach other and/or to arrange other components in a space between thesubstrates.

In a further embodiment of the first aspect, the semiconductor modulefurther comprises a printed circuit board including controllers and/ordrivers for the semiconductor devices. The printed circuit board isarranged in the space between the at least two substrates.

Thereby it is possible, for example, to provide an intelligent powermodule in which controllers and/or drivers of the semiconductor devicesare integrated.

The above object is also achieved in accordance with a second aspect.

According to the second aspect, a method of manufacturing asemiconductor module is provided. The method comprises preparing atleast two electrically insulating substrates, each having a first mainsurface and a second main surface opposite to the first main surface,mounting at least one semiconductor device on the first main surface ofeach of the substrates, connecting an external terminal to the firstmain surface of at least one of the substrates, and arranging the atleast two substrates opposite to each other so that their first mainsurfaces are facing each other.

With such a method it is possible, for example, to manufacture asemiconductor module in which heat generated by the semiconductordevices can efficiently be removed to both sides of the module. Further,by the improved heat dissipation and the arrangement of semiconductordevices at opposite sides of the module, the power density of asemiconductor module may be improved. Since the semiconductor devicesare only attached single-sided to the substrates, cost and processcomplexity can be kept low. The modules can be manufactured using wellestablished assembling technologies and therefore are potentiallylow-cost.

In an embodiment of the second aspect, the semiconductor module isfurther provided with an encapsulation, arranged in a way that thesecond main surfaces of each of the substrates are exposed on oppositesides of the encapsulation.

Thereby it is possible, for example, to protect the devices by anencapsulation and nevertheless be able to efficiently dissipate heatgenerated by the semiconductor devices from the opposite sides of themodule.

In a further embodiment of the second aspect, thermally conductivesubstrates are used as the substrates.

Thereby it is possible, for example, to better conduct heat dissipatedfrom the semiconductor devices to the outside of the module.

In a further embodiment of the second aspect, a power semiconductordevice is used as the at least one semiconductor device.

Thereby it is possible, for example, to apply the disclosure to powermodules for which efficiently dissipating heat is of a specialimportance.

In a further embodiment of the second aspect, the method furthercomprises mounting a heat sink to at least one of the second mainsurfaces of the substrates.

Thereby it is possible, for example, to further increase the efficiencyof dissipating heat from the semiconductor devices.

In a further embodiment of the second aspect, the external terminalcomprises at least two external leads. All the external leads arearranged to protrude in a plane from two opposite sides of the module,or all the external leads are arranged to protrude from a single side ofthe module, only.

Thereby it is possible, for example, to provide the connections to themodule in a plane at two opposite sides, which is a commonly usedarrangement for semiconductor devices, or to provide the connections tothe module on one side, only, leaving the other sides free for means fordissipating the heat.

In a further embodiment of the second aspect, a lead frame is connectedto at least two substrates as the external terminal.

Thereby it is possible, for example, to provide a variant of thesemiconductor module according to the disclosure.

In a further embodiment of the second aspect, bridges between individualleads of the lead frame are provided for interconnecting the at leasttwo substrates.

Thereby it is possible, for example, to easily provide interconnectionsbetween the at least two substrates.

In a further embodiment of the second aspect, two separate lead frame s,each connected to one of the at least two substrates are used as theexternal terminal.

Thereby it is possible, for example, to provide another variant of thesemiconductor module according to the disclosure.

In a further embodiment of the second aspect, individual leads of thetwo separate lead frame s are connected to each other forinterconnecting the at least two substrates.

Thereby it is possible, for example, to easily provide interconnectionsbetween the at least two substrates.

In a further embodiment of the second aspect, pins connected to one ofthe at least two substrates and protruding from the module at the sideopposite to the substrate to which the pins are connected are used asthe external terminal.

Thereby it is possible, for example, to provide another variant of thesemiconductor module according to the disclosure.

In a further embodiment of the second aspect, an internal lead frame orinternal pins are used for interconnecting the at least two substrates.

Thereby it is possible, for example, to easily provide interconnectionsbetween the at least two substrates.

In a further embodiment of the second aspect, the at least twosubstrates are arranged spaced apart from each other.

Thereby it is possible, for example, to avoid that the semiconductordevices or other components at the first sides of the substrates contacteach other and/or to arrange other components in a space between thesubstrates.

In a further embodiment of the second aspect, the method furthercomprises arranging a printed circuit board including driver circuitsfor the semiconductor devices in the space between the at least twosubstrates.

Thereby it is possible, for example, to provide an intelligent powermodule in which controllers and drivers of the semiconductor devices areintegrated.

It shall further be understood that an embodiment of the disclosure canalso be any combination of the dependent claims or above embodimentswith the respective independent claims or above aspects.

These and other aspects of the disclosure will be apparent andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a side view of a semiconductor module according to a firstembodiment of the present disclosure.

FIG. 1b is a perspectival view the semiconductor module according to thefirst embodiment.

FIG. 2a is a perspectival view of a first variant of a semiconductormodule according to any of the embodiments of the present disclosure.

FIG. 2b is a perspectival view of a second variant of a semiconductormodule according to any of the embodiments of the present disclosure.

FIG. 3a is a side view of a semiconductor module according to a secondembodiment of the present disclosure.

FIG. 3b is a perspectival view of the semiconductor module according tothe second embodiment.

FIG. 4a is a side view of a semiconductor module according to a thirdembodiment of the present disclosure.

FIG. 4b is a perspectival view of the semiconductor module according tothe third embodiment.

FIG. 5a is a side view of a semiconductor module according to a fourthembodiment of the present disclosure.

FIG. 5b is a perspectival view of the semiconductor module according tothe fourth embodiment.

FIG. 6a is a side view of a semiconductor module according to a fifthembodiment of the present disclosure.

FIG. 6b is a perspectival view of the semiconductor module according tothe fifth embodiment.

DETAILED DESCRIPTION

In the following, embodiments of the disclosure are described withreference to the enclosed figures.

FIGS. 1a and 1b show a semiconductor module 100 according to a firstembodiment, FIG. 1a in a side view and FIG. 1b in a perspectival view.For the sake of clarity, an encapsulation and a heat sink are omitted inFIG. 1 b.

The semiconductor module 100 comprises two electrically insulatingsubstrates 101 a, 101 b. Each substrate has two main surfaces oppositeto each other. Preferably, the substrates are thermally conductive. Thethermal conductivity of the material used may for example be in therange from 25 to 200 W/mK. For example, ceramic may be used as amaterial for the substrates. As a specific example, DCB substrates maybe used in which a sheet of copper is bonded to one or both sides of aceramic substrate. As another specific example, insulated metalsubstrates (IMS) may be used which have a metal baseplate, for examplemade of aluminum, on which an insulating layer, for example aceramic-filled polymer foil, and a metal foil, for example a copperfoil, are stacked in this order.

On a first main surface 102 a, 102 b of each of the substrates, one ormore semiconductor device(s) 110 is or are mounted. Preferably, thesemiconductor devices are power semiconductor devices such as, forexample, IGBTs, MOSFETs or diodes. For example, the bottom surface ofeach of the semiconductor devices is die-bonded, for example bysoldering or sintering, to a (not shown) wiring layer on the first mainsurface 102 a, 102 b of the corresponding substrate 101 a, 101 b, while(not shown) pads on the top surface of each of the semiconductor devices110 are bonded to (not shown) pads of the (not shown) wiring layer viabond wires 111 or clips.

According to the embodiments described in the present disclosure, thesubstrates 101 a, 101 b are arranged in the semiconductor module 100opposite to each other so that their first main surfaces 102 a, 102 bare facing each other. Thereby, a second main surface 103 a, 103 b ofeach substrates 101 a, 101 b, which is opposite to the first mainsurfaces 102 a, 102 b, faces towards the outside of the semiconductormodule 100. The substrates 101 a, 101 b are arranged spaced apart fromeach other so that the semiconductor devices 110 and/or bond wires 111do not contact each other.

For supplying power and signals from outside, an external terminal isprovided. In the present embodiment, the external terminal comprises alead frame 120. A lead frame is an arrangement of leads within a plane,surrounded by a frame. Even if during manufacturing, the frame is cutaway in order to separate the leads, the resulting arrangement of theexternal ends of the leads in a plane which is caused by their formerconnection to the planar frame also is generally called “lead frame” inthe art. In this meaning, the term is also used in the presentapplication. Only the relevant parts of the lead frame are shown in thefigures, not the complete lead frame.

The lead frame has a predetermined number of leads 121. In the presentembodiment, some of the leads 121 are bent downwards and some are bentupwards. Downwards and upwards in this context refers to the arrangementshown in FIG. 1a with the first substrate 101 a at the bottom and thesecond substrate 101 b at the top of the module.

The leads 121 a bent downwards are connected to the first substrate 101a and the leads bent upwards 121 b to the second substrate 101 b, forexample by soldering or sintering. Thereby, each of the substrates 101a, 101 b has an electrical connection to the outside. Additionally, thesubstrates 101 a, 101 b may also be electrically interconnected to eachother by means of bridges 122 that may be provided between adjacentleads 121 a, 121 b. FIG. 1b shows some leads 121 a, 121 b beinginterconnected by a bridge 122 as well as some leads 121 a, 121 bwithout a bridge.

The semiconductor module 100 further comprises an encapsulation 130,forming a package for the module. The encapsulation 130 is preferablymade of a resin and formed, for example, by transfer molding orinjection molding. The encapsulation 130 is formed in a way that thesecond main surfaces 103 a, 103 b of each of the substrates 101 a, 101 bare exposed on opposite sides of the encapsulation. In order to avoidresin from coming into contact with the second main surfaces 103 a, 103b, a film-assisted molding method may be used. During the molding, thebridges 122 preferably are over-molded so that they are protected andcannot be seen on the outside of the module.

On the exposed second main surfaces 103 a, 103 b of the substrates 101a, 101 b, a respective heat sink 140 a, 140 b may be mounted in order toimprove the heat dissipation.

Among others, the following effects can be achieved with a semiconductormodule as described above: Providing the substrates on opposite sides ofthe module with their second main surfaces exposed from theencapsulation increases the cooling area of the module. Compared to theprior approaches, such as those referenced in the introductory portionof this description, in which the second dissipating plate is connectedvia a spacer to the top side of the semiconductor devices on whichconnection pads are provided, the power dissipation can be improvedbecause the bottom sides of the semiconductor devices are directly andwithout spacer mounted on each of the substrates. Further, since thesemiconductor devices are arranged on both sides of the module, i.e. oneach of the substrates, the power density of the module can beincreased. Still further, since the power semiconductor devices are onlyattached single-sided to the substrates, the module can be manufacturedusing well established assembly technologies, and therefore cost andprocess complexity can be kept low.

FIG. 2 schematically shows different variants of a semiconductor module200. The variants differ from each other in the arrangement of the leadsof the external terminal.

The semiconductor module 200 a shown in FIG. 2a corresponds to thearrangement shown in FIG. 1. The two substrates 201 a are exposed fromthe encapsulation 230 a at the top and bottom of the module 200 a (thebottom side is not shown in the figure). The external terminal 220 acomprises a predetermined number of leads 221 a which protrude in aplane from two opposite lateral sides 231, 232 of the module 200 a.

The semiconductor module 200 b shown in FIG. 2b is a standing orvertical version. The leads 221 b of the external terminal 220 b allprotrude from a single side 233 of the module 200 b, only. This modulecan therefore vertically be inserted into a socket or a circuit board sothat the two substrates 201 b are exposed from the encapsulation 230 bat a front and (not shown) rear side of the module 200 b.

Even if a lead frame is described above as a means for electricallyconnecting the substrates to the outside and/or to each other, thepresent disclosure is not restricted to this specific example. Any othersuitable connecting technology may be used. Some further examples aregiven in the following embodiments.

FIGS. 3a and 3b show a semiconductor module 300 according to a secondembodiment, FIG. 3a in a side view and FIG. 3b in a perspectival view.For the sake of clarity, an encapsulation and a heat sink are omitted inFIG. 3 b.

The semiconductor module 300 differs from the semiconductor module 100shown in FIG. 1 in the arrangement of the external terminal. Instead ofa single lead frame, the external terminal comprises two separate leadframes 320 a, 320 b, each connected to one of the substrates 301 a, 301b. Thereby, each of the substrates 301 a, 301 b has an electricalconnection to the outside. Additionally, the substrates 301 a, 301 b mayalso be electrically interconnected to each other by connectingindividual leads 321 a, 321 b of the two separate lead frames 320 a, 320b to each other, for example by soldering or sintering. FIG. 3b showssome leads 321 a, 321 b being connected to each other as well as someleads 321 a, 321 b not connected to each other.

Other features of the second embodiment than those described above arethe same as in the first embodiment. Especially, each of the substrates301 a, 301 b has semiconductor devices 310 mounted thereon and isarranged so that the sides bearing the semiconductor devices 310 arefacing each other. The other sides of the two substrates are exposedfrom the encapsulation 330, and a heat sink 340 a, 340 b may be mountedthereon.

With the semiconductor module 300, the same effects can be achieved asdescribed above for the semiconductor module 100. Further, connectingthe individual lead frames to the individual substrates is facilitatedbecause the substrates need not be adjusted to each other during thatprocess.

FIGS. 4a and 4b show a semiconductor module 400 according to a thirdembodiment, FIG. 4a in a side view and FIG. 4b in a perspectival view.For the sake of clarity, an encapsulation and a heat sink are omitted inFIG. 4 b.

The semiconductor module 400 differs from the semiconductor module 100shown in FIG. 1 in the arrangement of the external terminal. Even if theexternal terminal also comprises a single lead frame 420, it isconnected to one of the substrates (first substrate) 401 a only.Thereby, this substrate 401 a has an electrical connection to theoutside. The other substrate (second substrate) 401 b is connected tothe first substrate 401 a and via the first substrate 401 a to theoutside by an internal lead frame 450.

During manufacturing, the internal lead frame 450 is first connected toone of the substrates, for example the second substrate 401 b, bysoldering or sintering. Then, the frame is cut away from the lead frame450, the substrate 401 b is flipped, and the lead frame 450 is connectedto the other substrate, for example the first substrate 401 a, bysoldering or sintering.

Other features of the second embodiment than those described above arethe same as in the first or second embodiment. Especially, each of thesubstrates 401 a, 401 b has semiconductor devices 410 mounted thereonand is arranged so that the sides bearing the semiconductor devices 410are facing each other. The other sides of the two substrates are exposedfrom the encapsulation 430, and a heat sink 440 a, 440 b may be mountedthereon.

The single leads of the lead frame 450 preferably have an elasticproperty such as a blade spring. During molding, the substrates therebyare elastically pressed against the walls of the mold, thus reducing therisk of mold resin bleeding on the exposed side of the substrates 401 a,401 b on which the heat sink 440 a, 440 b may be mounted.

With the semiconductor module 400, the same effects can be achieved asdescribed above for the semiconductor module 100.

FIGS. 5a and 5b show a semiconductor module 500 according to a fourthembodiment, FIG. 5a in a side view and FIG. 5b in a perspectival view.For the sake of clarity, an encapsulation and a heat sink are omitted inFIG. 5 b.

Similar to the semiconductor module 400 shown in FIG. 4, the externalterminal of the semiconductor module 500 also comprises a single leadframe 520, connected to one of the substrates (first substrate) 501 aonly. The other substrate (second substrate) 501 b is connected to thefirst substrate 501 a and via the first substrate 501 a to the outsideby means of internal pins 560.

During manufacturing, the internal pins 560 are first connected to oneof the substrates, for example the second substrate 501 b, by solderingor sintering. Then, the substrate 501 b is flipped, and the internalpins 560 are connected to the other substrate, for example the firstsubstrate 501 a, by soldering or sintering. Similar to the internal leadframe of the semiconductor module 400, the internal pins 560 may beprovided with a spring functionality.

Other features of the fourth embodiment than those described above arethe same as in the first to third embodiment. Especially, each of thesubstrates 501 a, 501 b has semiconductor devices 510 mounted thereonand is arranged so that the sides bearing the semiconductor devices 510are facing each other. The other sides of the two substrates are exposedfrom the encapsulation 530, and a heat sink 540 a, 540 b may be mountedthereon.

With the semiconductor module 500, the same effects can be achieved asdescribed above for the semiconductor module 100.

In a variant (not shown in the figures), pins may also be used for theexternal terminal instead of or additionally to the lead frame(s). Thepins are then connected to one of the substrates in an area opposite towhich the other substrate is not provided, and protrude from the moduleat the side opposite to the substrate to which they are connected.

FIGS. 6a and 6b show a semiconductor module 600 according to a fifthembodiment, FIG. 6a in a side view and FIG. 6b in a perspectival view.For the sake of clarity, an encapsulation and a heat sink are omitted inFIG. 6 b.

Similar to the semiconductor module 500 shown in FIG. 5, the externalterminal of the semiconductor module 600 also comprises a single leadframe 620, connected to one of the substrates (first substrate) 601 aonly. In addition to the two substrates, 601 a, 601 b, the semiconductormodule 600 also comprises a printed circuit board 670 which is arrangedin the space between the substrates 601 a, 601 b. The printed circuitboard 670 may for example include controllers and/or drivers for thesemiconductor devices 610 as well as other active and/or passiveelements.

Similar to in the semiconductor module 500, the first substrate 601 a isconnected to the printed circuit board 670 by means of internal pins661, and the second substrate 601 b is connected to the printed circuitboard 670 by means of internal pins 662. As an alternative, also the twosubstrates 601 a, 601 b may be interconnected by means of internal pinsat positions where the printed circuit board 670 is not provided orthrough holes in the printed circuit board 670. Further, the lead frame620 may also be connected to the printed circuit board 670 instead ofbeing connected to one of the substrates 601 a, 601 b. Instead of theinternal pins, internal lead frames may be used as in the semiconductormodule 400.

Other features of the fifth embodiment than those described above arethe same as in the first to fourth embodiment. Especially, each of thesubstrates 601 a, 601 b has semiconductor devices 610 mounted thereonand is arranged so that the sides bearing the semiconductor devices 610are facing each other. The other sides of the two substrates are exposedfrom the encapsulation 630, and a heat sink 640 a, 640 b may be mountedthereon.

With the semiconductor module 600, the same effects can be achieved asdescribed above for the semiconductor module 100. Further, anintelligent power module can be provided wherein controllers and/ordrivers of the semiconductor devices are integrated in the semiconductormodule.

The features of the embodiments described above may also be combined,where possible. For example, the different arrangements of the externalleads shown in FIGS. 2a and 2b may be applied to any of the aboveembodiments. As further examples, internal lead frames and/or internaland/or external pins as described with regard to the third and fourthembodiments and/or a printed circuit board as described with regard tothe fifth embodiment may also be used in combination with any of theother embodiments.

In summary, the present disclosure relates to a semiconductor module,especially a power semiconductor module, in which the heat dissipationis improved and the power density is increased. The semiconductor modulecomprises at least two electrically insulating substrates, each having afirst main surface and a second main surface opposite to the first mainsurface. On the first main surface of each of the substrates, at leastone semiconductor device is mounted. An external terminal is connectedto the first main surface of at least one of the substrates. Thesubstrates are arranged opposite to each other so that their first mainsurfaces are facing each other.

While the present disclosure has been illustrated and described indetail in the drawings and the foregoing description, such illustrationand description are to be considered illustrative or exemplary and notrestrictive. The disclosure is not limited to the disclosed embodiments.From reading the present disclosure, other modifications will beapparent to a person skilled in the art. Such modifications may involveother features, which are already known in the art and may be usedinstead of or in addition to features already described herein.

The disclosure has been described in conjunction with variousembodiments herein. However, other variations to the disclosedembodiments can be understood and effected by those skilled in the artin practicing the claimed disclosure, from a study of the drawings, thedisclosure and the appended claims. In the claims, the word “comprising”does not exclude other elements or steps, and the indefinite article “a”or “an” does not exclude a plurality. The mere fact that certainmeasures are recited in mutually different dependent claims does notindicate that a combination of these measures cannot be used toadvantage.

Although the present disclosure has been described with reference tospecific features and embodiments thereof, it is evident that variousmodifications and combinations can be made thereto without departingfrom the spirit and scope of the disclosure. The specification anddrawings are, accordingly, to be regarded simply as an illustration ofthe disclosure as defined by the appended claims, and are contemplatedto cover any and all modifications, variations, combinations orequivalents that fall within the scope of the present disclosure.

What is claimed is:
 1. A semiconductor module, comprising: at least twoelectrically insulating substrates, each having a first main surface anda second main surface opposite to the first main surface; for each ofthe substrates, at least one semiconductor device mounted on the firstmain surface of the corresponding substrate; a printed circuit board,the printed circuit board including controllers or drivers for thesemiconductor devices, wherein the printed circuit board is arranged ina space between the at least two substrates; and an external terminalconnected to the first main surface of at least one of the substrates;wherein the external terminal is formed as two separate lead frames,each connected to one of the at least two substrates; the at least twosubstrates are electrically interconnected by individual leads of thetwo separate lead frames being connected to each other; the substratesare arranged opposite to each other so that respective first mainsurfaces of the substrates are facing each other.
 2. The semiconductormodule according to claim 1, further comprising: an encapsulation,wherein the second main surfaces of each of the substrates are exposedon opposite sides of the encapsulation.
 3. The semiconductor moduleaccording to claim 1, wherein the substrates are thermally conductive.4. The semiconductor module according to claim 1, wherein the at leastone semiconductor device is a power semiconductor device.
 5. Thesemiconductor module according to claim 1, wherein a heat sink ismounted to at least one of the second main surfaces of the substrates.6. The semiconductor module according to claim 1, wherein the externalterminal comprises at least two external leads, and wherein: all theexternal leads protrude in a plane from two opposite sides of thesemiconductor module, or all the external leads protrude from a singleside of the semiconductor module, only.
 7. The semiconductor moduleaccording to claim 1, wherein the external terminal is formed as a leadframe connected to at least two substrates.
 8. The semiconductor moduleaccording to claim 7, wherein the at least two substrates areelectrically interconnected by bridges between individual leads of thelead frame.
 9. The semiconductor module according to claim 7, whereinthe at least two substrates are electrically interconnected by aninternal lead frame or by internal pins.
 10. The semiconductor moduleaccording to claim 1, wherein the external terminal is formed as pinsconnected to one of the at least two substrates and protruding from thesemiconductor module at the side opposite to the substrate to which thepins are connected.
 11. The semiconductor module according to claim 1,wherein the at least two substrates are arranged spaced apart from eachother.
 12. A method of manufacturing a semiconductor module, comprising:preparing at least two electrically insulating substrates, each having afirst main surface and a second main surface opposite to the first mainsurface; mounting at least one semiconductor device on the first mainsurface of each of the substrates; connecting an external terminal tothe first main surface of at least one of the substrates, wherein theexternal terminal is formed as two separate lead frames, each connectedto one of the at least two substrates, the at least two substrates areelectrically interconnected by individual leads of the two separate leadframes being connected to each other; arranging the substrates oppositeto each other so that respective first main surfaces of the substratesare facing each other; and arranging a printed circuit board in a spacebetween the at least two substrates, wherein the printed circuit boardincludes controllers or drivers for the semiconductor devices.